The pygmy right whale, a mysterious and elusive creature that rarely comes to shore, is the last living relative of an ancient group of whales long believed to be extinct, a new study suggests.

The findings, published today (Dec. 18) in the Proceedings of the Royal Society B, may help to explain why the enigmatic marine mammals look so different from any other living whale.

"The living pygmy right whale is, if you like, a remnant, almost like a living fossil," said Felix Marx, a paleontologist at the University of Otago in New Zealand. "It's the last survivor of quite an ancient lineage that until now no one thought was around."

The relatively diminutive pygmy right whale, which grows to just 21 feet (6.5 meters) long, lives out in the open ocean. The elusive marine mammals inhabit the Southern Hemisphere and have only been spotted at sea a few dozen times. As a result, scientists know almost nothing about the species' habits or social structure.